EP3649373B1 - Ring gear for an epicyclic or planetary reduction gear of a turbomachine - Google Patents

Description

Technical area :

The field of the present invention is that of turbomachines and more particularly that of differential transmission systems in these turbomachines, in particular planetary or planetary reduction gears.

State of the art :

The state of the art includes in particular the documents WO-A1-2010/092263 , FR-A1-2 987 416 , FR-A1-3 041 054 , US-A1-2016/097330 , which forms the basis of the two-part shape and EP-A1-3 109 412 .

Current turbomachines, in particular turbomachines comprising one or more propellers blowing a secondary flow, comprise a transmission system, called a reducer, to drive this or these propellers at the correct speed of rotation from the shaft of the power turbine of the primary body of the motor.

The operation of reduction gears, in particular on turbomachines with a fan propeller with a high bypass rate, requires a particularly high oil flow, of the order of 6000 to 7000 liters per hour at take-off, to ensure lubrication and cooling. of their gears and bearings.

Among the gearboxes used, there are planetary gearboxes and (with planetary gear) which have the advantage of offering high rates of reduction in the speed of rotation in reduced dimensions.

Such a reduction gear comprises a planetary pinion or central pinion, an outer ring gear and satellite pinions which mesh with the planetary pinion and with the ring gear, the support of one of these three components having to be locked in rotation for the operation of the gear train.

When the planet carrier is fixed in rotation, the central pinion and the crown are driving and driven, respectively, or vice versa. The reducer is then of the “planetary” type.

In the opposite case, of a reduction gear with an epicyclic gear train, the external crown is fixed in rotation and the central pinion and the planet carrier are leading and driven.

The main problem with this type of reduction gear is to ensure optimal meshing of each satellite on the one hand with the central pinion but also with the crown.

The crown extends around the axis of the reducer and comprises first and second coaxial annular elements and respectively comprising two internal annular teeth oriented differently and intended to cooperate with each satellite. The gear teeth of the crown are of the chevron type, the teeth of the elements having substantially opposite helix angles.

The annular elements of the crown comprise respectively first and second radially external annular flanges for fixing the elements to each other as well as to an annular crown holder intended to extend around at least part of the crown.

In the current technique, whether for an epicyclic or planetary architecture, it is difficult to ensure optimum centering of the elements, as well as of the crown carrier. This centering or axial alignment is important in order to minimize the misalignment of the teeth of the crown elements in operation. The geometry of the aforementioned flanges directly influences the misalignment of the teeth in operation. The elements tend to come together or move apart depending on the vibratory modes and the shapes of the teeth, the forces of which are transmitted to the crown carrier by the flanges of the crown. In addition, precise angular timing is necessary between the two elements in order to angularly index the teeth of the elements.

Centering solutions have already been proposed for a crown of this type. However, these solutions are not entirely satisfactory. The solution consisting for example in providing a peripheral rim at the internal periphery of the flange of one of the elements, which is intended to be engaged in an annular recess of complementary shape to the internal periphery of the flange of the other of the elements , is not satisfactory. Indeed, the presence of the flange and the centering recess in the vicinity of the teeth of the elements is likely to interfere with the transmission of forces in the elements and to cause different mechanical and vibratory behaviors of the elements in operation, and to result by misalignments of their teeth. Secondly, the centering from the inside of the elements prevents bringing the axial position of the webs of these elements closer to the median plane passing between the teeth. Furthermore, the oil used for the lubrication of the reduction gear in operation must be able to be evacuated and, when radial oil passages are provided through the ring gear, they generally result in radial notches in the centering flange, which are not necessarily regularly distributed around the axis and which can locally increase its flexibility to the detriment of its centering function. The object of the invention is to overcome at least some of the problems and drawbacks mentioned in the foregoing.

Presentation of the invention:

The invention relates for this purpose to an epicyclic or planetary reduction gear ring for a turbomachine, in particular an aircraft, said ring extending around an axis X and comprising first and second coaxial annular elements and respectively comprising two annular teeth internally oriented differently, each of said toothings comprising a pitch diameter and a median plane substantially perpendicular to said axis, and whose point of intersection is denoted Y in an axial section of the crown, said first and second annular elements further comprising respectively first and second radially external annular flanges for fixing said first and second elements together, as well as preferably to an annular crown holder intended to extend around at least a part of the crown, characterized in that each of said first and second flange comprises a peripheral part extending in an inclined plane with respect to said axis and passing substantially through said point of intersection Y.

In the present application, a "point of intersection" means a point of intersection between a pitch diameter of a toothing and a median plane of a toothing, this point of intersection being located in an axial section of the crown.

Furthermore, in the present application, the expressions “internal”, “external”, “interior”, “exterior”, etc. are understood to mean expressions referring to an axis of the turbomachine and in particular to the axis X of the crown of the reducer in the context of the present invention.

The flanges of the elements are thus shaped to optimize the paths of forces from the teeth to the zone for fixing the elements. The inclined plane can be better appreciated in two dimensions. In three dimensions, the inclined plane is rather a conical surface whose angle of the cone can vary with respect to the axis X. In this case, it can be considered that the peripheral part extending over an average fiber inclined with respect to the plane X and passing through point Y.

• ladite partie périphérique est une partie périphérique interne de chacune desdites première et seconde brides,
• ladite partie périphérique interne relie une partie périphérique externe sensiblement radiale de la bride correspondante, à une extrémité longitudinale d'un corps de l'élément correspondant,
• ledit corps est sensiblement cylindrique et comprend à sa périphérie interne ladite denture,
• lesdits corps sont à distance axiale l'un de l'autre ; ceci permet d'autoriser une rectification des dentures si elles ne sont pas coïncidentes, en passant un outil de rectification dans l'espace inter-corps ;
• lesdites parties périphériques inclinées ont chacune une surface périphérique interne qui s'étend radialement vers l'extérieur dans le prolongement d'une surface radiale d'extrémité du corps correspondant ; le prolongement jusqu'à la surface radiale d'extrémité du corps permet d'avoir un ensemble plus simple à usiner car pas il n'y a pas de rainure ou de gorge, et indirectement plus robuste, ce qui réduit les désalignements ;
• lesdites parties périphériques inclinées forment chacune un angle entre 0° et 90° par rapport audit axe, ce qui permet un chemin d'effort plus direct et de mieux répartir les contraintes ;
• lesdites parties périphériques inclinées délimitent entre elles une cavité annulaire inter-éléments de passage d'huile ; ceci permet à l'huile de ne pas stagner entre les parties périphériques inclinées ;
• lesdites parties périphériques inclinées ont une épaisseur sensiblement constante, ce qui permet une meilleure répartition des contraintes ;
• la position axiale des parties périphériques inclinées par rapport au plan d'appui des deux éléments annulaires est prédéterminée ; c'est la position et l'angle qui permettent de réduire le désalignement des dentures.

The crown according to the invention may comprise one or more of the following characteristics, taken separately from each other or in combination with each other:

• said peripheral part is an inner peripheral part of each of said first and second flanges,
• said internal peripheral part connects a substantially radial external peripheral part of the corresponding flange, to a longitudinal end of a body of the corresponding element,
• said body is substantially cylindrical and comprises at its inner periphery said toothing,
• said bodies are at an axial distance from each other; this makes it possible to authorize a rectification of the teeth if they are not coincident, by passing a rectification tool in the inter-body space;
• said inclined peripheral parts each have an inner peripheral surface which extends radially outwards in the extension of a radial end surface of the corresponding body; the extension to the radial end surface of the body makes it possible to have an assembly that is simpler to machine because there is no groove or groove, and indirectly more robust, which reduces misalignments;
• said inclined peripheral parts each form an angle between 0° and 90° with respect to said axis, which allows a more direct force path and better distribution of the stresses;
• said inclined peripheral parts delimit between them an annular cavity inter-oil passage elements; this allows the oil not to stagnate between the inclined peripheral parts;
• said inclined peripheral parts have a substantially constant thickness, which allows a better distribution of the stresses;
• the axial position of the peripheral parts inclined with respect to the support plane of the two annular elements is predetermined; it is the position and the angle which make it possible to reduce the misalignment of the teeth.

The present invention also relates to an epicyclic or planetary reduction gear for a turbomachine, in particular an aircraft, characterized in that it comprises a crown as described above.

Brief description of the drawings :

• La figure 1 représente schématiquement une coupe axiale d'une turbomachine utilisant l'invention.
• La figure 2 représente une vue détaillée en coupe d'un réducteur à train épicycloïdal.
• La figure 3 est une vue écorchée et en perspective du réducteur de la figure 2.
• La figure 4 est une vue partielle en coupe axiale d'un réducteur équipé d'une couronne selon l'invention.
• La figure 5 est une vue partielle en perspective de la couronne de la figure 4.
• La figure 6 est une section partielle axiale de la couronne de la figure 4.

The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the following description, with reference to the appended drawings in which:

• The figure 1 schematically represents an axial section of a turbomachine using the invention.
• The figure 2 shows a detailed sectional view of a planetary gear reducer.
• The picture 3 is a cut-away and perspective view of the gearbox of the figure 2 .
• The figure 4 is a partial view in axial section of a reduction gear equipped with a crown according to the invention.
• The figure 5 is a partial perspective view of the crown of the figure 4 .
• The figure 6 is a partial axial section of the crown of the figure 4 .

Description of an embodiment of the invention:

The figure 1 shows a turbomachine 1 which comprises, in a conventional manner, a fan propeller S, a low pressure compressor 1a, a high pressure compressor 1b, an annular combustion chamber 1c, a high pressure turbine 1d, a low pressure turbine le and a nozzle exhaust 1h. The high pressure compressor 1b and the high pressure turbine 1d are connected by a high pressure shaft 2 and form with it a high pressure body (HP). The low-pressure compressor 1a and the low-pressure turbine 1c are connected by a low-pressure shaft 3 and form with it a low-pressure body (LP).

The fan propeller S is driven by a fan shaft 4 which is coupled to the LP shaft 3 by means of a planetary gear reduction gear 10 shown here schematically.

The reducer 10 is positioned in the front part of the turbomachine. A fixed structure comprising schematically, here, an upstream part 5a and a downstream part 5b is arranged so as to form an enclosure E1 surrounding the reducer 10. This enclosure E1 is here closed upstream by joints at the level of a bearing allowing the crossing of the fan shaft 4, and downstream by seals at the level of the crossing of the LP shaft 3.

With reference to figure 2 and 3 , the reducer 10 comprises a crown 14 which is fixed via a support 20 to the fixed structure 5a, 5b with flexible means arranged to allow it to follow any movements of the fan shaft 4, in some degraded operating cases for example. In a planetary architecture, the support is made up of a more or less flexible part which drives the crown and a shaft part held by bearings or bearings and on which the fan is mounted. These fastening means are known to those skilled in the art and are not detailed here. A brief description can be found for example in FR-A1-2987416 .

The reducer 10 engages on the one hand on the shaft BP3 via splines 7 which drive a planetary gear pinion 11, and on the other hand on the fan shaft 4 which is attached to a planet carrier 13. Conventionally, the planet gear 11, the axis of rotation X of which coincides with that of the turbomachine, drives a series of planet gears or planet gears 12, which are regularly distributed over the circumference of the reducer 10. The number of planet gears 12 is usually set between three and six. The satellites 12 also rotate around the axis X of the turbomachine except in the case of a planetary where they rotate only around their axes of revolution, by meshing on internal teeth of the crown 14, which is fixed to a stator of the turbomachine by means of flanges 20 in the case of an epicyclic or fixed to a rotor of the turbomachine in the case of a planetary. Each of the satellites 12 rotates freely around a satellite axis 16 connected to the planet carrier 13, using a bearing which may be smooth, as shown on the figure 2 , or a bearing with rolling elements (ball or roller bearings).

The rotation of the satellites 12 around their satellite axis 16, due to the cooperation of their pinions with the teeth of the crown 14, causes the rotation of the planet carrier 13 around the axis X, and consequently that of the fan shaft 4 which is linked to it, at a speed of rotation which is lower than that of the BP shaft 3.

The figure 2 watch, with picture 3 , the routing of the oil to the reducer 10 and its path inside the latter. Arrows show on the figure 2 the path followed by the oil from, in this example, a buffer tank linked to the fixed structure of the turbomachine, to the pinions and the bearings to be lubricated. The lubricating device conventionally comprises three parts: a first part linked to the fixed structure and delivering the oil to the rotating parts of the reducer 10, a rotating wheel with the planet carrier 13 receiving this oil in the case of an epicyclic and a distributor assembled to the planet carrier, which are fixed on a planetary architecture, and oil distribution circuits supplied with oil by the impeller to convey it to the places to be lubricated.

The figures 4 to 6 illustrate an embodiment of a crown 114 according to the invention.

Crown 114 extends around an axis which is axis X of reduction gear 110 and of the turbomachine, and comprises two coaxial annular elements, called first annular element 114a or upstream element and second annular element 114b or downstream element.

Each element 114a, 114b comprises an annular body 114aa, 114ba of generally cylindrical shape and connected to an annular flange 114ab, 114bb extending radially outwards.

Each body 114aa, 114ba includes an internal annular toothing 150 at its internal periphery. Although this is not visible in the drawings, the teeth 150 of the two bodies or elements are complementary to the teeth of the satellites, which are of the type shown in picture 3 . The teeth 150 of the elements 114a, 114b are herringbone.

Each toothing 150 comprises an external diameter passing through its external periphery, an internal diameter passing through its internal periphery, as well as a pitch diameter D which is measured substantially at mid-height or mid-radial dimension of the toothing. Furthermore, P denotes a median plane of each set of teeth, this plane being substantially perpendicular to the aforementioned axis and passing substantially in the middle of the set of teeth in the axial direction.

The body 114aa, 114ba of each element is connected by a longitudinal end to the corresponding flange 114ab, 114bb. The body 114aa is connected at its downstream end, located on the side of the other body 114ba, to the flange 114ab, and the body 114ba is connected at its upstream end, located on the side of the other body 114aa, to the flange 114bb .

Each flange 114ab, 114bb has the general shape of a dihedral and comprises two peripheral parts, respectively internal 114ab1, 114bb1 and external 114ab2, 114bb2.

The outer peripheral parts 114ab2, 114bb2 extend substantially perpendicular to the axis and therefore have a substantially radial orientation. They are intended to bear axially on each other and thus each comprise a radial annular bearing surface 152.

The parts 114ab2, 114bb2 are used to fix the elements 114a, 114b to each other, as well as to a crown holder 154 in the example shown.

For this, the parts 114ab2, 114bb2 each comprise an annular row of through axial orifices 156 for passage of fastening means 158 of the screw-nut type or the like. The orifices 156 of the parts 114ab2, 114bb2 are aligned and receive the fixing means 158.

The crown holder 154 also includes an annular flange 160 for fixing to the flanges 114ab, 114bb and in particular to the parts 114ab2, 114bb2. The flange 160 is applied axially to one of the parts 114ab2, 114bb2, namely here the part 114ab2 of the upstream element 114a. Part 114ab2 is thus inserted axially between flange 160 and part 114bb2. The reverse is also possible. By reverse, we mean that the crown carrier is on the right side of the crown, which represents the rear of the engine.

The flange 160 comprises holes aligned with the holes 156 and which also receive the fixing means 158, the heads of which can be applied axially on the downstream face of the part 114bb2 and nuts can be applied axially on the upstream face of the flange 160 or vice versa. In the example shown, a flange 162 of an annular oil recuperator rests axially on the part 114bb2 and receives the heads of the nuts on its downstream face.

The parts 114ab2, 114bb2 further comprise a first set of axial holes 163 through and tapped allowing the disassembly of the crown holder 154 with the crown 114. A second set of axial holes 163 through and tapped makes it possible to disassemble the element 114a from the element 114b. Parts 114ab2, 114bb2 also include at least one pin 165 for angular setting of elements 114a, 114b. Each part 114ab2, 114bb2 can include one or more of these holes 163, intended to be aligned with one or more similar hole(s) 163 of the other part, and to receive a wedging 165. The pin 165 here has a generally cylindrical shape and is oriented axially. It comprises an external annular bead, substantially in its middle in the axial direction, and intended to be located substantially at the level of the surfaces 152 of the flanges.

The part 114bb2 comprises at its outer periphery a cylindrical centering rim 164. This rim 164, which is carried by the element 114b is configured to cooperate by axial sliding and radial support with the outer periphery of the other element 114a to ensure the centering, during assembly and in operation, of this other element 114a. As a variant, element 114a could comprise such a rim intended to cooperate with element 114b with a view to centering it.

The rim 164 is intended to cooperate with the outer periphery of the flange 114ab of the element 114a, and in particular with the radially outer free annular edge of its part 114ab2. On assembly, the rim 164 thus extends around the part 114ab2.

In the example shown, the flange 164 also ensures the centering of the crown holder 154. The flange 164 can cooperate as indicated above with the outer periphery of the flange 160.

The rim 164 here extends continuously over 360°. It is thus neither split nor sectorized. The reference surface for centering is thus uninterrupted.

The internal peripheral parts 114ab1, 114bb1 are inclined with respect to the axis X of the crown 114. The part 114ab1 extends radially from the upstream to the downstream in the direction of the outside, and the part 114bb1 extends from upstream to downstream towards the interior. In the example shown, the parts 114ab1, 114bb1 are inclined from 0° to 90° with respect to the axis X, and preferably between 30 and 60° and delimit an annular cavity 166 with a section of generally triangular shape, the point is oriented radially outward. Their axial positions are such that the average fiber passes through the intersection of the median plane of the toothing as well as its pitch diameter.

The parts 114ab1, 114bb1 make it possible to connect the parts 114ab2, 114bb2 to the bodies of the elements 114aa, 114bb. Due to the orientation of the parts 114ab1, 114bb1 and their connection to the longitudinal ends, respectively downstream and upstream, of the bodies 114a, 114b these bodies are spaced axially from each other by a predetermined distance.

Lubricating oil is intended to flow in operation through this inter-body space and to enter the cavity 166. Substantially radial passages are provided between the flanges 114ab, 114bb in order to allow the evacuation of the radially outward from the crown.

The oil passages here are formed on the one hand by substantially radial notches or slots 168 formed in the surfaces 152 of the flanges. Each flange includes an annular row of notches 168 axially aligned with notches 168 on the other of the flanges. The notches are made at a distance from the orifices 156 through which the fixing means 158 pass, from the pin hole 165 as well as from the holes 163. Each notch has, for example, in section a semi-circular (semi-oblong) or rectangular shape as in the example shown ( figure 5 ).

The notches are in fluid communication, at their radially inner ends, with the cavity 166, and at their axially outer ends with oblong-shaped oil outlet through-orifices 170 formed in the centering flange 164. In other words, the passages of oil emerge at their radially outer ends on the outer cylindrical surface of the rim 164, to form therein orifices 170 for the oil outlet.

The figure 6 shows a partial axial section of the reducer 110 in which Y denotes the intersection between the plane P and the pitch diameter D for each toothing 150. As can be seen in the drawing, the internal peripheral part 114ab1, 114bb1 of each flange extends in a plane passing substantially through the point of intersection Y. This position as well as the aforementioned inclination are two important parameters in this embodiment.

Each internal peripheral part 114ab1, 114bb1 has an internal peripheral surface 115a which extends radially outwards in the extension of a radial end surface 115b of the corresponding body. The axial distance between the surfaces 115b corresponds to the inter-element distance and the maximum axial dimension of the cavity 166.

The internal peripheral parts 114ab1, 114bb1 have a substantially constant thickness.

With the exception of the flange 164, the crown elements 114a, 114b are symmetrical with respect to a median plane, perpendicular to the axis and passing substantially between the elements.

The crown 114 according to the invention is easier to produce, to mount as well as to control than those of prior technologies.

Claims (10)

1. Ring gear (114) for an epicyclic or planetary reduction gear (110) for a turbine engine, in particular of an aircraft, said ring gear extending around an axis X and comprising first and second coaxial annular elements (114a, 114b) and comprising respectively two inner annular teeth sets (150) of different orientation, each of said teeth sets having a pitch diameter (D) and a median plane (P) substantially perpendicular to said axis, and the intersection point of which is designated Y in an axial cross-section of the ring gear, said first and second annular elements further comprising respectively first and second radially outer annular flanges (114ab, 114bb) for attaching said first and second elements to each other, characterised in that each of said first and second flanges comprises a peripheral portion (114ab1, 114bb1) extending in a plane that is angled with respect to said axis X and that passes substantially through said intersection point Y.
2. Ring gear (114) according to the preceding claim, wherein said peripheral portion is an inner peripheral portion (114ab1, 114bb1) of each one of said first and second flanges (114ab, 114bb).
3. Ring gear (114) according to the preceding claim, wherein said inner peripheral portion (114ab1, 114bb1) connects a substantially radial outer peripheral portion (114ab2, 114bb2) of the corresponding flange to a longitudinal end of a body (114aa, 114ba) of the corresponding element.
4. Ring gear (114) according to the preceding claim, wherein said body (114aa, 114ba) is substantially cylindrical and comprises at its inner periphery said teeth set (150).
5. Ring gear (114) according to the preceding claim, wherein said bodies (114aa, 114ba) are at an axial distance from one another.
6. Ring gear (114) according to one of claims 3 to 5, wherein said angled peripheral portions (114ab1, 114bb1) each have an inner peripheral surface (115a) that extends radially outwards in the extension of an end radial surface (115b) of the corresponding body (114aa, 114ba).
7. Ring gear (114) according to one of the preceding claims, wherein said peripheral portions (114ab1, 114bb1) each form an angle between 0° and 90° with respect to said axis X.
8. Ring gear (114) according to one of the preceding claims, wherein said angled peripheral portions (114ab1, 114bb1) delimit between them an inter-element annular cavity (166) for the passage of oil.
9. Ring gear (114) according to one of the preceding claims, wherein said angled peripheral portions (114ab1, 114bb1) have a substantially constant thickness.
10. Epicyclic or planetary reduction gear (110) for a turbine engine, in particular of an aircraft, characterised in that it comprises a ring gear (114) according to one of the preceding claims.

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